Re: XProc-based rasterizer

Hi,

Thanks Norm and John for comments so far. After reflection, I don't
actually regard this as a casting problem but a rendering problem, at least
when inputs are SVG. :-)

In any case since the same host of questions asked by Norm arises also in
the XSL-FO context, I am exploring that option.

Apparently FOP can be made to do this (i.e., produce PNG), perhaps I can
get that written to the file system somehow.
 I am looking at prior art as documented here:
https://www.oxygenxml.com/pipermail/oxygen-user/2011-June/003664.html

This is what I have so far, with an SVG document on the input port:

<p:insert
match="/descendant::fo:instream-foreign-object[@id='svg-placement']"
position="first-child">
    <p:with-input port="insertion" pipe="source@make-png-from-svg"/>
    <p:with-input port="source">
        <fo:root>
            <fo:layout-master-set>
                <fo:simple-page-master master-name="svg"
                    page-height="{$height}" page-width="{$width}">
                    <fo:region-body/>
                </fo:simple-page-master>
            </fo:layout-master-set>
            <fo:page-sequence master-reference="svg">
                <fo:flow flow-name="xsl-region-body">
                    <fo:block>
                        <fo:instream-foreign-object id="svg-placement"/>
                    </fo:block>
                </fo:flow>
            </fo:page-sequence>
        </fo:root>
    </p:with-input>
</p:insert>


The question will be how to invoke the formatter to do the right thing.

Since I also have some animal bones on the fire (er, beef short ribs in a
braise), this is as far as I have made it so far today.

If you know already this won't work (even producing a PNG file as a side
effect), I'll be interested in more details.

Thanks! Wendell





On Fri, Mar 7, 2025 at 12:39 PM Norm Tovey-Walsh <ndw@nwalsh.com> wrote:

> John Dziurlaj <john@turnout.rocks> writes:
> > I'm not sure casting content types would be enough to fully effectuate a
> cast that is inherently lossy. When casting from a vector to raster image,
> resolution, color spaces, bit depths, aliasing among other things need to
> be considered. Such nuances could be handled via option parameters, but
> those are implementation-defined.
>
> I fear even in a rasterize step, some of those are going to be
> implementation-defined parameters. Different raster formats support
> different color spaces, may support limited resolutions or bit depths, etc.
>
> What would the “general” parameters be, I wonder?
>
> - Size
>   - If width and height are provided, does that change the aspect ratio?
> - Resolution
> - Color
>   - Bit depth? Color space? I’m not even sure what the options are
>
> > There is also the question of which set of casts are supported by a
> given XProc processor. Built for purpose steps on the other hand give a
> clear contract as to which functionalities are available and which aren't.
>
> I agree. I think a step is the better answer here.
>
>                                         Be seeing you,
>                                           norm
>
> --
> Norm Tovey-Walsh <ndw@nwalsh.com>
> https://norm.tovey-walsh.com/
>
> > The one serious conviction that a man should have is that nothing is to
> > be taken too seriously.--Nicholas Butler
>


-- 
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